Precise measurements of the refractive indices for dielectrics using an improved Brewster angle method

Abstract

We propose a simple and accurate experimental method for finding the refractive index of solid and liquid dielectrics using the polarization of light reflected by a dielectric surface near the Brewster angle. This experiment can be implemented in an optics laboratory at the undergraduate or graduate level. The method improves the precision of the determination of the Brewster angle by more than two orders of magnitude compared with recent measurements, but uses similar optical components. An angular resolution of 0.01° can be easily achieved using a parabolic fit of the parallel component of the reflectance normalized to the total reflectance in a region close to the Brewster angle, which leads to values of the refractive index for solid and liquid dielectrics with a precision of 10−4. Care is taken to eliminate the instabilities in the laser beam and the time dependence from our measurements. We report results for two glasses and for isopropyl alcohol for several wavelengths in the visible range. The latter is used as a test of our procedure due to its shallow dispersion in the visible.